Sensitive material



Patented Dec. 7,1943

SENSITIVE MATERIAL John Russell, Rochester, N. Y., assignor to EastmanKodak Company, Rochester, N. Y., a corporation of New Jersey 1Application April 25, 1940, Serial No. 331,641

4 Claims.

This invention relates to a new photographically sensitive material. Ihave found that it is possible to form, preferably in the surface ofpaper of the quality ordinarily used for photographic purposes, metallicsalts of the cellulose of the fibers of the paper, which salts aresensitive to light, heat or electrical stimuli and capable of havingphotographic images formed and developed therein. In particular I havefound that mercury and silver salts give the best results but thatbismuth, iron, uranium, copper, lead, thallium and other metal saltsgive positive results. When I speak of the paper as photographicallysensitive, I use the expression in a broad sense to includeresponsiveness, not only to light radiations, but to chemical andelectrical stimuli whereby a visible image may be made or reproduced.

The resulting sensitive paper may be used in various ways. In particularit is useful in industrial recorders of the type where a heated stylusis brought into contact with the paper, in place of an inked pen orpointer.

The preparation of the paper is ordinarily carried out in two steps:first, submitting it to an oxidizing bath or to an oxidizing atmosphere,and then to a solution of a metal salt wherein the carboxyl takes up themetallic ion and forms the sensitive salt.

Various examples of methods of forming the sensitive surfaces will firstbe given and then the properties and methods of treatment of thesesurfaces will be described.

The paper is bathed at room temperature in a solution of equal parts ofconcentrated sulfuric acid and of Water saturated with potassiumdichromate, for a period of time of the order of 30 to 60 seconds. It isthen washed, until free from sulfate and dried. The paper at this stageis heat sensitive and a legible mark will be produced upon it by astylus heated to a temperature of from 250 to 300 C. passing over it ata speed of from .1 to 1.5 millimeters per, second, the image being apale brown. Oxidation for an even shorter time, say seconds, willproduce a heat sensitivity that is readily detectable.

The paper may also be treated in an oxidizing atmosphere, or cellulosefibers may be oxidized in the manner described in the patent of Edwin C.Yackel and William O. Kenyon, No. 2,232,990, granted February 25, 1941,and then coated as a layer upon a sheet of paper or other material. Asexplained in that patent, the product resulting from oxidizing thecellulose with NO: is a combined uronic acid resulting from theoxidation of the hydroxyl on the primary carbon atoms of theanhydroglucose units to carboxyl, or in other words, the final productis an anhydroglucuronic acid. When this material is combined with heavymetal, as specified herein, a salt which is sensitive to heat or lightis obtained. Moreover, the oxidized fibers could be treated beforecoating with a metallic salt solution, as hereinafter described, so thatthe layer is sensitive when formed on the paper support.

The paper with an oxidized surface layer is then bathed in a metallicsalt solution, such as silver or mercurous acetate aqueous solution ofless than 1 per cent concentration for a period of time which is not atall critical and may vary widely,.for instance from a half minute toover thirty minutes. It is then washed and dried. The resulting paper ismuch more sensitive and will show a legible mark from a stylus at atemperature at 300 C. moving at a speed of 8 to 10 mm. per second. Thesecond bath is given under dark-room conditions, a filter absorbing onlyblue and violet light being used.

Referring to the accompanying drawing, Fig. 1 shows an enlarged sectionof a sheet of paper I, the surfaces 2 of which have been treated in themanner described to form in the superficial fibers sensitive metallicsalts of carboxylic groups produced on the cellulose, and Fig. 2 shows asimilar section of a support 3; such as paper, upon one surface of whichhas been formed by coating a layer 4 of metallic salts of cellulose.

Other salt solutions than those mentioned may be used, in each case thesolution being one per cent, or saturated if the solubility is less than1 per cent, some of the solutions giving useful results being mercuricnitrate, mercurous nitrate, silver nitrate, ammonium metavanadate,ammonium molybdate, ferric nitrate. The mercury and silver salts gaveoutstandingly good results. Other solutions giving legible marks only ata very slow speed, were bismuth acetate, bismuth nitrate, cobaltousacetate, cuprous chloride, cupric acetate, ferric acetate, lead acetate,lead nitrate, manganous acetate, thallous acetate, uranium acetate,uranium nitrate.

The papers made as above described were also tested for their printingout properties when exposed to a Cooper Hewitt quartz mercury vapor arcoperaitng at a potential drop of volts across its terminals and thosecontaining mercury or silver gave strong images in less than one minuteexposure at a distance of 30 cm. from such an arc while those containingbismuth, iron or uranium yielded a faint image after a minute exposure.

Some of the papers also were found to have a photothermographicproperty, that is the property of yielding a visible image when heatedfollowing exposure to light. In those containing mercury, this wasparticularly noticeable, while it was less in those containing bismuth,copper, lead or thallium.

It was also found that the papers containing mercury or silver werecapable of having images chemically developed therein, followingexposure to light, in a 2 per cent hydroquinone solution containing 1per cent acetic acid, or in an M. Q. developer.

The paper should be of high quality purified cellulose, but I have foundthat results vary widely between different papers, so that any data heregiven are to be taken as typical and illustrative of results found inactual experiments with certain samples of paper.

What I claim is:

1. A product sensitive to heat and/or light essentially consisting of apaper sheet surfaced with a salt of anhydroglucuronic acid and a metalselected irom the group consisting of mercury, silver, vanadium,molybdenum, iron, bismuth,

ten

cobalt. copper, lead, manganese, thallium, and uranium.

2. A photographically sensitive product comprising a sheet composed ofcellulose fibers, at least one surface of said sheet having thereon aphotosensitive material essentially consisting oi metallic salts ofcellulose carboxylic groups, said groups having been produced onsuperficial fibers of said sheet by oxidation thereof and being capableof having a visual image formed thereon lby the action of heat, light,or electrical stimu- 3. A photographic product comprising a sheetcomposed of cellulose fibers, one surface of said

